1. Field of the Invention
The present invention relates to a gas analyzer and a method for the analysis of a gas with respect to one or more gaseous components of the gas of the type wherein a gas sample is diverted from a gas to be analyzed.
2. Description of the Prior Art
When a gas is to be analyzed, a sample of the gas is commonly diverted to a measuring unit, e.g., a gas analyzer. One such method and gas analyzer are described in U.S. Pat. No. 4,509,359. This patent describes a method in which a continuous gas sample is diverted from a breathing gas during the ventilation of a patient's lungs. The gas sample is sent to a gas analyzer in which the concentration of, e.g., carbon dioxide or the like is determined. The gas sample is then discharged into ambient air or a collection container.
Modern ventilators and respirators, such as, e.g., the Servo Ventilator 300 from Siemens-Elema AB, Sweden, are able to control flows to/from a patient with great accuracy. They are also capable of regulating very small flows, a necessity, e.g., in the treatment of neonatal infants. With these ventilators, the removal of even a small gas sample will affect the flow to the patient and, in particular, will affect the regulation of inspiratory and expiratory flows.
Gas analyzers wherein a gas sample is extracted from the breathing gas and then returned to the breathing gas after measurement are known in the art. Some analysis procedures, however, can affect and alter one or more of the component gases. For example, oxygen can be measured with a high-temperature electrochemical cell. Any anaesthetic gases mixed with the breathing gas might then be chemically altered. In such a case, the analyzed gas cannot be returned to the breathing gas.